The adapter
Your model may be calling tools that your serving stack throws away
A serving adapter moved a BFCL v4 tool-call rate from 0.00 to 0.96, with the model, its weights and its seed unchanged. Parsed calls went from none to 636 in the same comparison, the preprint’s authors report.
A score of zero on this benchmark is more likely to be your parser than your model.
The adapter turns the model’s raw output into structured tool calls. Where its expected format and the model’s emitted format disagree, well-formed calls are discarded before anything counts them, so the evaluation records a capability failure that never happened.
The authors do not say how many published tool-use numbers were produced behind a mismatched adapter, which is the figure that would say how much of the literature this touches.
What it changes Before concluding a model cannot call tools, log what the adapter received and what it emitted. A near-zero score is a parser hypothesis first and a capability finding second.